


let me be your taste test

by wrenhera



Category: Haikyuu!!
Genre: Bottom Miya Osamu, Dildos, Incest, M/M, Sibling Incest, Size Kink, Stomach Bulge, Top Miya Atsumu
Language: English
Status: Completed
Published: 2020-12-20
Updated: 2020-12-20
Packaged: 2021-03-11 05:02:02
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,826
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28189644
Author URL: https://archiveofourown.org/users/wrenhera/pseuds/wrenhera
Summary: Osamu has a size kink.
Relationships: Miya Atsumu/Miya Osamu
Comments: 27
Kudos: 430





	let me be your taste test

Osamu had always been a bit of a size queen. Since the moment he realized he liked getting fucked, he knew this. He liked the feeling of being stuffed so full he could barely move, how the stretch felt, and the idea of someone bigger than him fucking him until he cried was the fastest way to get him hard. Unfortunately, he had been blessed with a large, muscular body, and even more unfortunately, so had his twin. 

He knew it was wrong to look at Atsumu that way, but he couldn’t help but stare at the way Atsumu’s thighs bulge as he squatted to set the ball to him, at how broad his shoulders were, the way he could easily bench Osamu if he tried. But the worst part was his dick, much larger than average and with Atsumu’s lack of shame in the locker room and at home, unable to be avoided. Osamu knew he was the same size, being twins and all, but something about it seemed bigger on Atsumu, so much more imposing. 

So here he was, sitting on their bedroom floor with a gigantic dildo in his hands, wishing it was his brother instead. It was obviously much larger than a normal dick, specially made to go deeper than anything real ever could, and Osamu shivered in anticipation. The reviews online had even said that it was big enough to cause stomach bulges, but he doubted it. He had watched enough stomach bulge porn that he knew it was possible, but the idea of it happening to him was too good to be true. He was a lot bigger than the twinks online excitedly posting about how amazing it had been for them. 

Osamu rose up on his knees and carefully positioned himself over the dildo. It was massive, almost terrifyingly large from this angle, but some part of that excited him. He lowered himself slowly, a delicious shiver running through him when it brushed against his hole and missed, sliding against it instead. He grabbed the dildo to steady it, groaning as it finally began to breach him. 

If it looked big, it felt even bigger. The slight burn of his ass stretching around the toy left him breathless. His thighs shook with the effort it took to keep himself kneeling, to keep himself from accidentally taking the cock all at once and hurting himself. He had to take it slow, at least for now. It felt like it would never end, like he would keep sinking down on it forever, but finally he found himself seated completely. 

Sure, it felt good, but more heady was the idea of what he had just done. It was impossibly deep inside of him. He had never felt so full before, his mind reeling as he thought about his insides contorting to accommodate the huge toy. He leaned back, moaning as it pressed even harder against his prostate. He could feel the toy pushing up from the inside against his stomach, and he was amazed to see a small bulge there when he looked down. He slowly started rocking himself on the dildo, watching in awe as the bulge moved in tandem. He had never been so turned on in his life. 

“Hey, ‘Samu, you home?” he heard Atsumu say, opening the door suddenly. “Got outta practice ear-” 

The words died out as Atsumu locked eyes on Osamu, kneeling in the middle of their bedroom absolutely impaled on a monster dildo. They stared at each other for a moment. Osamu was so shocked he didn’t even think to cover up. He blushed deeply, but couldn’t break eye contact with Atsumu. 

After what felt like an eternity, Atsumu said, “... Ya gonna keep goin’?” 

“What?” Osamu’s mouth felt dry. 

“I said, ya gonna keep goin’? ‘Cause I can go if ya want to, or…” He shifted awkwardly, breaking their gaze to look at his feet. “Or I could stay.” 

“W-why would ya stay?” Osamu couldn’t stop himself from grinding against the base of the dildo a bit, its rippled texture feeling amazing, and having a living, breathing, real Atsumu here rather than a fantasy one was making his brain go nuts. 

He looked at Osamu again, lips pulled into a slight smile. “‘Cause,” Atsumu moved closer, “ya look really hot like this.” 

Osamu searched his face for signs that this was some kind of sick joke, that Atsumu was just fucking with him, but there was none to be found. In fact, Atsumu was breathing more heavily than usual, flushed the same way Osamu got when he was turned on. Atsumu looked down at his stomach then looked back up excitedly. 

“Fuck, it’s that deep inside ya?” Atsumu asked, his expression equal parts shocked and aroused. Osamu nodded, then rose up a little on the toy to show how big it was, shivering as he sunk back down. “Holy shit, yer taking it so well.” The praise lit up something in Osamu’s brain and he let out a quiet whimper. Atsumu’s hands twitched where they were by his sides. He reached towards Osamu, then stopped. “Can I touch?” 

“Please,” Osamu gasped, and Atsumu grabbed hold of Osamu’s hips. He immediately started a steady pace, fucking Osamu on the cock more aggressively than he was ready for, and he moaned in shock at the sensation of the toy moving in and out of him roughly. He scrabbled his hands against the carpet for a moment before clutching onto Atsumu’s back desperately, pressing his face into the crook of Atsumu’s neck. 

“That’s it, just let me take care of ya,” Atsumu said, voice low. Has it always been that low? Osamu pushed his face harder into Atsumu’s neck, muffling his moans as his body was pushed, pulled, used to wring as much pleasure out of him as possible. “Were ya thinkin’ about me, ‘Samu? Wishing this were my cock filling ya up so nice?” 

Osamu’s brain short-circuited for a second, not prepared to hear something that filthy come from his brother’s mouth. Atsumu stopped suddenly, Osamu’s hips moving on their own to seek some kind of release. Osamu whined, embarrassed at his own reactions but unable to stop, needing Atsumu to move him again. “Please, ‘Tsumu, why’d ya stop?” 

“Wanna hear you,” Atsumu said before pulling away, getting behind Osamu instead and grabbing his waist again. He put his legs on either side of Osamu’s, pulling him in close enough that he could feel Atsumu’s hard cock against his back. Atsumu started back up his relentless pace, but now there was no way for Osamu to stop the noises that came out of him, nowhere to hide his face. Tears pricked his eyes from how overwhelming the situation was, his brother coming out of nowhere to give him what he had always wanted, and he felt his body go limp against Atsumu. Atsumu took his body weight easily, holding him upright and continuing to fuck him. He nudged Osamu’s head until it lolled to one side, nuzzling his face into Osamu’s exposed neck.

Atsumu pressed a hand against Osamu’s stomach, marveling at the feeling of the toy bulging against his palm with every thrust. He pushed Osamu as far as he could go down on the dildo, ignoring Osamu’s cries as he rubbed his thumb across the bump. It moved back and forth under his ministrations, and if Osamu’s whimpers were to be believed, it must have felt good. “That feel nice?” 

“Feels-” Osamu jolted as Atsumu prodded a little harder than before, moaning loudly. “F-feels, uh, it’s-” He was panting, trying his best to answer but his mouth couldn’t catch up to the thoughts racing through his head. “It’s a lot.” 

“Still good?” Osamu nodded furiously, then rolled his hips against Atsumu’s in frustration. Atsumu groaned and pulled back, much to Osamu’s displeasure. “Hold on, hold on, just gimme a sec,” Atsumu said, pulling down his track shorts so that his dick could have a bit of relief. It slid down Osamu’s ass and he let himself thrust a few times against it, shivering at Osamu’s needy whimpers. He held Osamu even closer, nestling his dick into the space between their bodies so that every time Osamu moved on the toy, he would feel it too. 

Atsumu started moving him again, changing the angle every so often until he found the one that seemed to drive Osamu wild. Osamu started making little guttural noises, like his moans were getting caught in his throat, and Atsumu couldn’t get enough of them. “You gonna cum soon? Ya think you can cum without me touching yer cock?” Osamu nodded, tears streaming down his face. 

“T-tsumu,” he mumbled, then gasped as Atsumu sped up the pace. “Tsumu, fuck, f- too much, ah-” 

“Ya want me to stop?” 

Osamu shook his head violently, finally moving his hands from where they were threaded into the carpet to grip Atsumu’s thighs harshly. “‘m so close, don’t stop.”

“God, yer such a slut for me, aren’t ya?” Atsumu couldn’t stop his mouth, the words coming out without him even realizing. “Does it get ya off, me knowing how desperate you are to get fucked? Knowing how ya like to get filled up with cocks so big they make your stomach bulge?” He kept slamming Osamu down, each thrust punctuated by Osamu’s gasps and sobs. “Ya wanna be used so bad, don’t ya? I think you were made to be fucked, ‘Samu, yer practically beggin’ for it. Can’t wait ‘til it’s me inside you instead.” 

At that, Osamu went completely rigid, back arching as he came hard all over his chest and the floor. He slumped back down into Atsumu’s arms and Atsumu started grinding against him in earnest, cumming quickly and messily all over Osamu’s back. Osamu was panting loudly, his cheeks flushed and hair matted against his forehead. Atsumu held him carefully, making sure he wasn’t putting all his weight on the dildo so that he wouldn’t accidentally hurt himself. 

After a bit, Osamu began shifting his hips uncomfortably, so Atsumu guided him forward until the dildo slid completely out of him. Atsumu couldn’t believe how big it was, able to see its full girth now that it wasn’t inside Osamu, and he felt something akin to pride at how well his baby brother had taken it. He scooped up Osamu and moved him to the bed, hoping his knees weren’t too scraped up by the carpet. 

Osamu’s eyes were closed, so Atsumu assumed he had passed out sometime between cumming and the bed, but as soon as he moved to start cleaning up the mess that was their bedroom floor, Osamu mumbled, “Can you hold me?” 

Atsumu knew they would have to talk about this at some point, but for now he was content in squeezing into the tiny twin bunk next to Osamu and holding him until they both fell asleep. 

**Author's Note:**

> Things I knew going into this fic: I think stomach bulges are hot  
> Things I now know coming out of this fic: hnnnnmnghghh atsumu and osamu.... BIG
> 
> hmu on twitter @wrenhera!


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